I'm going to sound uber noob here. I have the two one-inch slots (I know that's irrelevant) and another slot that resembles the bottom three in your picture more than the top one. It's about the same length as the bottom three but the little tick is on the left side (like the top one) instead of on the right side (like the bottom three). I hope that made sense.
If you managed to decode my retarded explanation up there ^^, do I have a PCI Express 2.0 x16 slot?
I'm not sure what's more important here, the length of the slot or where the tick mark is.
And since I accidentally edited out the link in my OP, I'll repost it here.
On a side note, I just realized the card I've been looking at has several bad reviews, mostly the card overheating or just failing altogether within days or weeks after purchase. If my budget is about $100, I'm wondering if I'm just better off with this card as it's reviews are spectacular.